I've seen people use just a regular ol' Supermask under their bridles as well. I do like the style of the kind Appylover linked to. But whenever I notice a fly on my horse while riding, it's always just below the eyes...so that type probably wouldn't swish away the flies located there.
KittenVal, the kind you linked looks like nice coverage, but I wonder if it might be a pain to put on/take off...
I love mine but I got it from Chashel.
You can get it with or without ears and with or with out a long nose flap to cover the nostrals.
My horse would go out on the trail and violently toss his head from the flys to the point where he wasn't even walking in a straight line. Now we have no problems and I am confident enough to put other people on him for trails with no worries.
I got UltraShield Fly Bonnet with Ears at TSC on weekend (same as at jeffersequine.com). I was thinking about standard bonnet, but it doesn't cover the eyes. My both horses are already run crazy from flies even in ring. :(